Phase III study shows PRT 4445 meets endpoint as Antidote-Portola Pharma

Portola Pharmaceuticals announced topline results from the first part of the Phase III ANNEXA-R (Andexanet Alfa a Novel Antidote to the Anticoagulant Effects of FXa Inhibitors � Rivaroxaban) study, which is evaluating the safety and efficacy of PRT 4445 (andexanet alfa) with the Factor Xa inhibitor Xarelto (rivaroxaban). Results showed that the study met its primary endpoint with high statistical significance. Andexanet alfa administered as an intravenous (IV) bolus significantly and immediately reversed the steady-state anticoagulation activity of Xarelto and was well tolerated.

41 healthy volunteers were given Xarelto 20 mg once daily for four days and then randomized in a 2:1 ratio to receive at Cmax either andexanet alfa administered as an 800 mg IV bolus (n=27) or to placebo (n=14). The study achieved its primary endpoint with high statistical significance. Results showed that andexanet alfa significantly and immediately reversed the anticoagulation activity of Xarelto. Andexanet alfa was shown to be well tolerated. The Company expects to present the full data set at the American College of Cardiology's Annual Scientific Session. The second part of the ANNEXA-R study, which is evaluating a bolus plus a continuous infusion of andexanet alfa to sustain reversal, is ongoing.

Comment: Andexanet alfa is a first-in-class recombinant, modified Factor Xa molecule that directly reverses the effects of Factor Xa inhibitors in patients who suffer an uncontrolled bleeding episode or who require emergency surgery.